To provide more dense memory for computing operations, concepts involving memory devices (which may be referred to as 3D stacked memory, or stacked memory) having a plurality of closely coupled memory elements have been developed. A 3D stacked memory may include coupled layers or packages of DRAM (dynamic random-access memory) memory elements, which may be referred to as a memory stack. Stacked memory may be utilized to provide a great amount of computer memory in a single device or package, where the device or package may also include certain system components, such as a memory controller and CPU (central processing unit).
As 3D stacked memory devices are increased in size, there are varying temperatures through the memory stack. The inner part of a 3D memory stack will generally be hotter than the outer portions since only the outer portions are exposed to cooling, and a larger stack will generally result in a higher temperature difference between the inner and outer portions.
The operation of a memory changes as the memory is heated. In particular, a memory generally requires more frequent refresh cycles at higher temperatures.
However, lower cost memory may not include thermal sensors, or may not provide thermal data. Without thermal sensing, it is difficult to determine how heat is spread throughout a memory device, and thus how to appropriately handle refresh operations.